Apparatus and method of treating tabs of printed circuit boards and the like

ABSTRACT

Printed circuit boards are carried generally vertically, along a path, with the tabs at the lower end being immersed in an electrolyte. The boards are automatically conveyed through opposed serially arranged pairs of rollers, which drive them along their path. Brushes wipe the boards to prevent contact with electrolyte above the desired contact level, as they are conveyed along the path. The solution is constantly replenished and turbulence provided by delivering electrolyte solution, with insoluble metallic ions in it, by pumping the solution from a sump, through an array of nozzles along each side of the path, thus providing fresh electrolyte along with providing turbulence to the electrolyte. The nozzles are charged at a sufficiently low level to avoid their destruction. Electrical contact is made with the printed circuit boards, by means of serially engaging the boards with spring fingers of a continuous conductor along each side of the boards as they are conveyed along their path, and thereby conducting the applied charge to the immersed tabs, whereby the tabs function as cathodes for electrodeposition of metallic ions thereon. The drive for the boards is provided by means of opposed pairs of rollers. One roller in each pair is a driving roller, with the opposing roller functioning as an idler, but forming an interference fit between the rollers as the boards are carried therebetween.

BACKGROUND OF THE INVENTION

In the art of printed circuit board manufacture, it is known to platetabs of the boards with various substances, particularly gold, andgenerally after first nickel plating prior to gold striking and plating,for the purpose of obtained better resistivity, high conductivity at theconnection points defined in the tabs, and high corrosion resistance.Such techniques have frequently experienced problems in driving theprinted circuit boards, positively along their path, and insatisfactorily applying the electrolyte to the tabs, in sufficientdensity, during the residence time of the tabs in the solution.

SUMMARY OF THE INVENTION

The present invention is addressed to making good electrical contactwith the printed circuit boards, to positively driving the boards alongthe board path, with their tabs immersed, and to delivering theelectrolyte to the vicinity of the tabs, by means of delivery nozzleslocated along the tab path, with the nozzles functioning as electrodes.

Accordingly, it is a primary object of this invention to provide a novelelectroplating apparatus, for electroplating tabs of printed circuitboards.

It is a further object of this invention to accomplish the above object,wherein the electroplating of the tabs, involves the electrodepositionof gold onto the tabs.

It is another object of this invention to accomplish the methodsestablished by the apparatus discussed above.

It is another object of this invention, to provide for adjustabilitywith respect to the drive of boards through their paths, whereby boardsof different thicknesses may be accommodated.

It is a further object of this invention to make electrical contact withprinted circuit boards, at their upper ends, outside of contact with theelectrolyte, but to provide for adjustability of such contact, in orderto accommodate boards of various heights.

It is another object of this invention to deliver printed circuit boardsalong their paths through treatment stations.

It is another object of this invention to accomplish the above objects,wherein the boards are appropriately guided during their movement alongthe path.

Other objects and advantages of the present invention will be readilyapparent to those skilled in the art by reading of the following briefdescriptions of the drawing figures, detailed descriptions of thepreferred embodiments and the appended claims.

BRIEF DESCRIPTIONS OF DRAWING FIGURES

FIG. 1, is a vertical sectional view, taken longitudinally through theapparatus of this invention, generally along the line I--I of FIG. 2,and wherein a number of printed circuit boards are shown, being conveyedfrom right to left as viewed in FIG. 1, with the tabs at the lower endsof the boards at a level for immersion in the electrolyte bath, and withthe illustration in FIG. 1, being broken, to shorten the samelongitudinally as a drafting expedient.

FIG. 2 is a transverse vertical sectional view, of the apparatus of FIG.1, taken generally along the line II--II of FIG. 1, wherein the boarddrive wheels, the nozzles, and the electrical contact means for theboard, together with their adjustment, are all clearly illustrated.

FIG. 3 is an enlarged fragmentary plain view of the drive apparatus, fordriving the boards through their predetermined paths, and is takengenerally along the line III--III of FIG. 2, with portions beingillustrated in section.

FIG. 4 is an enlarged fragmentary horizontal sectional view, withportions broken away for the sake of clarity, taken through theboard-engaging conductors and their conducting spring fingers, with theview of FIG. 4 being taken generally along the line IV--IV of FIG. 2.

FIG. 5 is an enlarged fragmentary horizontal sectional view, takenthrough the apparatus of this invention, generally on line V--V of FIG.2, and wherein the drive and idler wheels are illustrated for moving theboard along its path, with the bank of idler wheels having means foradjustably positioning the wheels.

FIG. 6 is an enlarged fragmentary horizontal sectional view, takenthrough the board as it is being conveyed along its path through theelectrolyte and with an array of nozzles being illustrated, in section,along each side of the board path.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail, reference is first made to FIG.1, wherein the tab plating apparatus is generally designated by thenumeral 20 as comprising left and right end walls 21 and 22, side walls23 and 24, sump bottom 25, and top cover 26. Elongated vertical slots 27and 28 are provided in walls 22 and 21, respectively, for accommodatingingress and egress of printed circuit boards 30, being received with theapparatus 20, and being delivered therefrom, in the direction of flow,along the predetermined path that will be apparent hereinafter, and asindicated by arrow 31 in FIG. 1.

The electrolyte 32, is present in the sump defined by the walls 21through 24, and sump bottom 25.

Electrolyte is pumped from the sump 32, by means of pumps (not shown)located in the sump 32, and delivered, up through delivery lines 33 and34, located inside, but close to the walls 24 and 23, respectively, torespectively associated manifolds 35 and 36. A plurality of such lines33 or 34, deliver electrolyte to the manifolds 35 and 36.

Elongated arrays of nozzles banks 37 and 38 extend horizontally betweeninlet and outlet walls 22 and 21, as illustrated in FIGS. 1 and 2, eachwith nozzles 40 connected therewith and disposed along side the path oftravel of the lower end of the printed circuit board 30 being deliveredtherepast, whereby electrolyte can be discharged through orifices 41 ofthe nozzles 40, to impinge upon both sides of the boards 30.

The nozzle banks 37 and 38, are located in the bath 43, below the liquidlevel 44 thereof, and are provided with electrolyte pumped underpressure, through suitable nipples 45, held in seated position inopenings 46, by means of collars 47, in threaded engagement withthreaded members 48, that in turn are in threaded engagement with elbows50, that communicate with the manifolds 35 or 36.

Electrolyte is therefore delivered from the sump 32, via lines 33, 34,via manifolds 35, 36, via elbows 50, via members 48, via nipples 45, vianozzle banks 37, 38, and out through the orifices 41 of nozzles 40,while the nozzles 40 are immersed in electrolyte in the bath zone 43,below the level 44, and with the delivery of electrolyte through thenozzle orifices 41 serving to create a turbulence within the bath zone43, for enhancing uniform distribution of insoluble ions carried in acidsolution, throughout the bath zone 43.

It will be noted that the rate of flow of the electrolyte into the bathzone 43, is at a sufficiently high level, to maintain the liquid level44, and that overflow ports 51, at the level 44, through walls 52 and 53of the trough that forms the bath zone, enable return of electrolyteback into the sump 32, outside trough walls 52 and 53, forrecirculation. Electrolyte return holes 55 may also be provided in thebottom wall 56 of the trough 54, for facilitating greater flowthrough ofelectrolyte into the sump 32, and to increase the agitation provided byelectrolyte flow in the bath zone 43.

It will be noted that a plurality of lower guide rollers 57 arerotatingly carried on shafts 58, in an elongated groove 60, of aU-shaped track member 61, extending between the walls 22 and 21, andsupported from the bottom 56 of the trough 54, by means of verticalstandards 62. The rollers 57 function as idlers, and together with theupper inside portions of the upstanding legs 63, serve to guide thelower ends of the printed circuit boards 30, as they travel through theapparatus 20.

With particular reference to FIG. 1, it will be apparent that a maskedportion or stripe 65, is provided, spaced upwardly slightly from thelower ends of each of the printed circuit boards. The mask 65 may be anadhesively secured sheet, or may be a paint-like substance that has beenapplied, where illustrated on the boards, across conductor portions ofthe boards, to define a zone, below which plating is desired, but abovewhich plating is not desired. Accordingly, the mask zone 65 serves torestrict the passage of electrolyte to those portions of the boards 30below the mask zones 65.

It will be noted that the nozzle orifices 41 are illustrated in FIG. 1as being disposed at a level for plating of tab portions 66 of boards30, as they are conveyed therepast.

At about the level of the mask zones 65 of the boards 30, it will benoted that longitudinally extensive wipers, 67 are provided. Thesewipers 67 are of the multiple filament brush type, constructed to bestiff, but yet to yieldably engage opposite sides of the printed circuitboards 30 being conveyed therepast, as illustrated in FIG. 2, and abovethe level 44 of electrolyte or bath, to wipe from the boards 30, invicinity of the mask zones 65, any electrolyte that may have beenspashed onto, or otherwise come into contact with the boards 30 in thezones of mask 65.

The wipers 67 extend generally longitudinally, between the walls 21 and22, and are carried in suitable holders 68, of the transversecross-section illustrated in FIG. 2. The holders 68 are carried onopposite sides of the path of board flow, at the lower ends of upperbath zone cover 70 and 71.

Pairs of opposed drive wheels 72 and 73 are provided, along the path offlow of printed circuit boards, between the inlet and exit openings 27and 28, respectively, with the rollers 72, 73 being on opposite sides ofthe path, and with the roller 73 being the idler roller in eachinstance, and with the roller 72 being the drive roller in eachinstance, and with the spacings between rollers 72 and 73 being setrelative to the thickness of a given printed circuit board 30, suchthat, in each instance, there is an interference fit between the rollers72 and 73 when a printed circuit board 30 is disposed between them. Inthis instance, only one of the rollers 72 or 73 in each pair, needs tobe driven. It will also be noted that the rolling surfaces of therollers 72 and 73, are provided with a resilient nonconductive coatingmaterial, for assuring good grip with the printed circuit boards 30during their conveyance through the apparatus 20.

The idler rollers 73 are carried in a suitable mounting block 74 ofC-shaped cross section, by means of a shaft 75 extending between legs 76and 77 of the mounting block 74. The block 74 has a plurality of slottedholes 77 therein, for receiving connector members 78 therethrough, withthe lower ends of the connector members 78 being in threaded engagementat 80, in upper plate 70. It will be apparent that the mounting block 74may be adjustably positioned, as desired, toward and away from the pathof movement of printed circuit boards 30 between the rollers, such thatthe bank of rollers 73 may be moved closer to, or farther away from therollers 72, by simple loosening of threaded members 78 andre-positioning of the mounting block 74, as desired.

The drive rollers 72 are fixedly mounted, on drive shafts 82, lower endsof which are bushing-mounted at 83, in upper member 71, and with theshafts 82 being driven, for positively rotating the drive wheels 72.

The upper ends of the shafts 82 have bevel gears 84 carried thereon,that in turn are in meshed engagement with bevel gears 85 carried onmain drive shaft 86, that, in turn, is driven by a suitable motor 87.

Horizontal support member 87, carried by wall 24, having bushings 88therein, supports the upper ends of the shafts 82, and gears 84 carriedthereon, as well as supporting shaft supports 90 that, in turn, journalthe main drive shaft 86.

An upper guide track 92, is provided, constructed, so as, in transversesection, as viewed in FIG. 2, to be of inverted U-shaped cross section.The track 92 extends between inlet and outlet walls 22 and 21,respectively, of the apparatus 20, as illustrated in FIG. 1, and asprovided with depending legs 93 and 94, connected by web 95. At theupper end of the opening 96 in the track 92, there are provided aplurality of upper guide rollers 97, for engaging the upper ends 98 ofthe boards 30, and guiding boards 30 in their movement along the paththrough the apparatus.

The rollers 97 are of the idler type, mounted for rotation on shafts100, with protruding shaft portions in engagement with opposite legs 93,94, of the track member 92.

Below the guide wheels 97, in the track 96, on each side of the path ofmovement of the printed circuit boards 30 therebetween, there areprovided elongate continuous conductors 103, extending from one end wall22 of the apparatus, to the other 21. These conductors 103 areelectrically connected, each by means of suitable lead lines 104,through the track member 92, to conduct electricity to the upper ends ofthe printed circuit boards 30, through a plurality of serially disposedspring fingers 105, that are incompletely severed from the conductors103, and extend inwardly to engage opposite sides of the printed circuitboards 30, as the boards are delivered therepast, with the springfingers 105 being in biased engagement with the opposite side of theboards being delivered therebetween. The spring fingers 105 thusspringingly engage the boards 30, and make electrical connection withthe upper ends of the boards, along their conductive portions. Theconductive portions of the upper ends of the boards conventionallycommunicate with the tabs 66 at the lower ends of the boards, as printedcircuit boards are designed. In order to accommodate printed circuitboards 30 of varying vertical heights, the track 92 that houses theguide rollers 97 and the elongate conductors 103 therein, is capable ofbeing adjustably positionable at various heights. To this end the trackmember 92 is provided with a plurality of tapped holes 108 therein,along its length, for receiving, in threaded engagement therein, aplurality of threaded connectors 110. The threaded connectors areadapted to be slidingly positionable along vertical slotted holes 111,in track support 112, that, in turn, is carried by upper wall 26. Asufficient number of track supports 112 are provided along the length ofthe track, to carry the same.

It will be apparent that the means for imparting electrical connectionto the upper ends of the printed circuit boards, as well as the meansfor guiding the upper ends of the printed circuit boards, are thereforeall capable of being adjustably positioned vertically, withoutdisturbing the drive for the drive rollers 72.

The apparatus 20 may comprise a plurality of modules connected together,end-to-end, in accordance with the principles and connection means ofU.S. Pat. No. 4,015,706. To this end, the modules may be provided withdowel pins 120, for alignment of modules one to the other, by insertionof the pins 120 into mating holes 121, of a next adjacent module. Also,mounting blocks 122 may be utilized, having tapped holes 123 therein,for connection by means of threaded members, of a module having amounting block 122 along each side, with an adjacent end of anext-adjacent module, by means of the threaded members that engage thetapped holes 123, passing through holes 124 of a next-adjacent module.In this manner, connection and alignment means is provided, frommodule-to-module. Also, the drive rod 86 may be constructed to besubstantially coextensive with the length of the apparatus 20, betweenwalls 22 and 21 thereof, as a single drive rod. The ends of the driverods may be likewise connected by a plugging type connector member, inaccordance with the disclosure of U.S. Pat. No. 4,015,706, the diclosureof which is herein incorporated by reference.

A filter may be provided for the electrolyte in the sump 32, whichfilter may be movably disposed therein, in accordance with thedisclosure of U.S. Pat. No. 3,776,800, the disclosure of which isincorporated by reference.

It will be apparent from the foregoing, that the conductor portions ofthe plates themselves 30, function as electrodes, with respect to thoseportions of the plates 30, that comprise the tab portions 66 that are tobe electroplated. These tabs 66 will generally comprise the cathodes.The anodes will preferably be the nozzles 40, and preferably thecomplete nozzle banks 37, 38, and connector members 45 and 47,electrically connected to a suitable power source by means of the leads49. It will further be understood that generally an AC power source willbe utilized, converted by means of a rectifier (not shown) to a suitablesource.

It will further be understood that, while the disclosure above isprincipally directed toward electroplating gold in the form of insolublegold ions in the electrolyte, onto the tabs 66 of printed circuitboards, as part of the electroplating process, it will be understoodthat apparatus in accordance with the structure of apparatus 20 may beutilized to perform preliminary functions, prior to the actual goldelectroplating. For example, solutions other than electrolytes may beutilized in apparatus 20, such as degreasing solutions, whereby theprinted circuit boards would be delivered to a next adjacent module,where perhaps a nickel plating would take place, in accordance with theelectroplating techniques taught herein. Thereafter, the goldelectroplating may take place, followed by suitable rinsing, blow-dryingoperations, as may be necessary to complete the entire process.

It will also be understood that, with respect to the electricalconnection with the printed circuit boards, at the upper ends, thatsuitable materials, may be employed. For example, the guides that formthe track 92 may be of polypropylene construction, as desired, as may bethe guide member 61 that forms the lower guide track.

It will be apparent also that various other modifications may beemployed in the apparatus of this invention, for example, baffles may beutilized in the bath 43, for obtaining desired flow situations, as maybe desired. Additionally, aside from those components that actuallyfunction as electrodes, the various components of this apparatus,particularly those in the bath and in the immediate vicinity of thebath, will either be coated with, or comprised of electricallynonconductive material.

It will also be apparent that while this process is directed towardelectroplating gold onto tabs of plates, the equipment and techniquesdisclosed herein may be utilized for electroplating other metals ontoprinted circuit board portions, or even onto other members that are tobe electroplated, if such other members have the necessary structuralfeatures to accommodate use in the apparatus of this invention.Accordingly, various modifications may be made in the details ofconstruction, as well as in the use and operation, all within the spiritof the invention as defined in the appended claims.

What is claimed is:
 1. Apparatus for localized electroplating of tabs ofprinted circuit boards and the like, comprising:means defining a bathzone of electrolyte; conveying means for conveying printed circuitboards such that tabs on lower ends thereof are carried through the bathzone, with the boards in generally upright disposition along apredetermined generally vertical path; delivery means for delivering asufficient flow of electrolyte to the bath zone, to maintain a bathdepth of a predetermined desired level; means disposed above saidpredetermined level, for wiping the printed circuit boards againstelectrolyte contact above the level of said wiping means; meansautomatically and serially engaging portions of the boards that are outof solution and making continuous electrical contact therewith as boardsare conveyed through the solution, whereby the immersed board tabsfunction as electrodes; said delivery means including a bank ofelectrolyte delivery nozzles along said path; means making electricalconnection with said nozzles, whereby said nozzles function as immersedelectrodes; means for generating an electrical potential between saidelectrodes.
 2. The apparatus of claim 1, wherein said nozzles areinsoluble in an electrolyte and are anodically charged at a sufficientlylow potential to avoid nozzle destruction.
 3. The apparatus of claim 1,wherein said nozzles and wiping means are disposed both sides of thepath of movement of boards thereby.
 4. The apparatus of claim 1, whereinsaid wiping means comprise brushes of nonconductive material.
 5. Theapparatus of claim 1, wherein said conveying means comprise a pluralityof opposed roller pairs along said path outside of said bath zone, withone roller of each said pair being mounted on each side of said path,for board engagement therebetween.
 6. The apparatus of claim 5, whereinthe opposed rollers of each said pair have resilient board-engagingsurfaces and are mounted for rotation relative to each other to be ininterference fit with a board upon receiving a board therebetween. 7.The apparatus of claim 5, wherein one roller in each said pair is adriving roller and the other roller in each said pair is an idlerroller, with a plurality of said idler rollers being mounted forrotation in a common frame, and wherein means are provided foradjustably positioning said frame laterally toward and away from saidpath, for accommodating boards of different thicknesses.
 8. Theapparatus of claim 1, wherein said means for making electrical contactwith the boards includes an elongate continuous conductor carried bymounting means on each side of the upper end of said board path, withsaid conductors each having a plurality of conductive spring fingerscarried serially thereby and extending transversely into the path of theupper ends of said boards for making electrical engagement with saidboards.
 9. The apparatus of claim 1, including means for verticallyadjustably positioning the means for making electrical contact with theupper ends of the boards, for accommodating boards of different heights.10. The apparatus of claim 8, including means for vertically adjustablypositioning the means for making electrical contact with the boards, foraccommodating boards of different heights, wherein said elongatecontinuous conductors are carried in a track, and wherein said track isadjustably positionable vertically.
 11. The apparatus of claim 1,including upper guide rollers for guiding the upper ends of the boards,in their movement along their path.
 12. The apparatus of claim 1,including lower guide rollers for guiding the lower ends of the boards,in their movement along their path.
 13. The apparatus of claim 10,including upper guide rollers for guiding the upper ends of the boardsin their movement along their path, and wherein said rollers aredisposed in said track, above said conductors.
 14. The apparatus ofclaim 1, wherein said delivery means comprises overflow means fordischarging electrolyte from said bath zone above the predetermineddesired level, sump means for collecting electrolyte thus discharged,and pump means for pumping electrolyte from said sump means to saidnozzles.
 15. The apparatus of claim 2, wherein said nozzles and wipingmeans are disposed along both sides of the path movement of boardsthereby, and wherein said wiping means comprises brushes ofnonconductive material, and wherein said conveying means comprise aplurality of opposed roller pairs along said path outside of said bathzone, with one roller of each said pair being mounted on each side ofsaid path, for board engagement therebetween, and wherein the opposedrollers of each said pair have resilient board-engaging surfaces and aremounted for rotation relative to each other to be interference fit witha board upon receiving a board therebetween, and wherein one roller ineach said pair is a driving roller and the other roller in each saidpair is an idler roller, with a plurality of said idler rollers beingmounted for rotation in a common frame, and wherein means are providedfor adjustably positioning said frame laterally toward and away fromsaid path, for accommodating boards of different thicknesses, andwherein said means for making electrical contact with the boardsincludes an elongate continuous conductor carried by mounting means oneach side of the upper end of said board path, with said conductors eachhaving a plurality of conductive spring fingers carried serially therebyand extending transversely into the path of the upper ends of saidboards for making electrical engagement with said boards, includingmeans for vertically adjustably positioning the means for makingelectrical contact with the boards, for accommodating boards ofdifferent heights, and including upper guide rollers for guiding theupper ends of the boards, in their movement along their path, includinglower guide rollers for guiding the lower ends of the boards, in theirmovement along their path, wherein said delivery means comprisesoverflow means for discharging electrolyte from said bath zone above thepredetermined desired level, sump means for collecting electrolyte thusdischarged, and pump means for pumping electrolyte from said sump meansto said nozzles.
 16. The method of localized electroplating of tabs ofprinted circuit boards and the like, comprising the steps of:providing abath zone of electrolyte; conveying printed circuit boards through thebath, in generally upright disposition, along a predetermined generallyvertical path, with the tabs being carried through the bath; deliveringthrough a bank of nozzles along the path to the bath zone, a sufficientflow of electrolyte, to maintain a bath depth of a predetermined desiredlevel; wiping the printed circuit boards against electrolyte contact asthey are delivered along their path, with the wiping being done at alevel just above that of the bath depth; automatically and seriallyengaging portions of the boards and making electrical contact therewithout of the level of the bath, as the boards are carried through thebath, thereby making the board tabs function as electrodes in theelectrolyte bath; making an electrical connection with the nozzles andcausing them to function as immersed electrodes, and generating anelectrical potential between the electrodes.
 17. The method of claim 16,including the steps of guiding the printed circuit boards along theirupper and lower edges as they are carried along the path.
 18. The methodof claim 16, including the steps of engaging the printed circuit boardsin interference fit relation serially, by means of rollers, for drivingthe boards along their path.
 19. Apparatus for localized treatment oftabs of printed circuit boards and the like, comprising:means defining atreatment zone; conveying means for conveying the tabs of printedcircuit boards on lower ends thereof, through the treatment zone, withthe boards in generally upright disposition along a predeterminedgenerally vertical path; delivery means for delivering a treatment fluidto boards in the treatment zone; with said conveying means comprising aplurality of opposed roller pairs along said path outside of saidtreatment zone, with one roller of each said pair being mounted on eachside of said path, for board engagement therebetween; and with theopposed rollers of each said pair having board-engaging surfaces and aremounted for rotation relative to each other to be in board-grippingrelationship with a board upon receiving a board therebetween, and withsaid delivery means including means for driving rollers.
 20. Theapparatus of claim 19, wherein one roller in each said pair is a drivingroller and the other roller in each said pair is an idler roller, with aplurality of said idler rollers being mounted for rotation in a commonframe, and wherein means are provided for adjustably positioning saidframe laterally toward and away from said path, for accommodating boardsof different thicknesses.